1. Field of the Invention
The present invention generally relates to an automatic document feeding mechanism for use in an image recording machine such as a copying machine or a laser printer and, more particularly, to the automatic document feeding mechanism of a type wherein sheet-like documents to be copied can be automatically transported successively from a document storage unit towards a document reading station and then from the document reading station back to the document storage unit.
2. Description of the Related Art
The U.S. Pat. No. 4,313,673 discloses an automatic document feeding mechanism of the type referred to above. This prior art automatic document feeding mechanism is so designed and so operable that the lowermost one of sheet-like documents to be copied which are stacked on a document support tray can be drawn outwardly from the document support tray for the transportation thereof towards a document reading station at which an image on the lowermost document can be scanned, and, after the image on the lowermost document has been scanned at the document reading station, it can be returned to the document support tray so as to lie atop the stack of the remaining sheet-like documents.
During the successive circulation of the sheet-like documents from the document support tray back to the document support tray past the document reading station, it is often experienced that, if the next succeeding, or second-fed, document is transported from the document reading station to the document support tray before the first-fed document is returned to the document support tray with its trailing ends completely received within the document support tray, the second-fed document may squeeze into between the documents supported on the document support tray and the trailing end of the first-fed document, resulting in a possible problem that subsequent copies would be made out of order. On the other hand, if a sufficient length of time is provided between the timing of complete return of the first-fed document into the document support tray and the start of feed of the second-fed document towards the document reading station, the number of copies afforded by the image recording machine for each unit time will be reduced.
Also, even though the length of time between the timing of complete return of the first-fed document into the document support tray and the start of feed of the second-fed document is chosen to be of a value effective to avoid the above discussed inconvenience, it may often occur that, during the return of the first-fed document into the document support tray, the first-fed document may be transported in a skewed fashion and/or in a relationship generally jammed with the previous document and, therefore, the second-fed document may be squeezed in beneath the first-fed document.